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Case Study 7: Mr and Mrs Kirrage 

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Janet and her husband bought 16 panels for their home, together with an Everhot 150i in Graphite, in 2015.

They live in sunny Truro and have a large four-bedroom, three-bathroom house. The 16 panels deliver 4kW with each panel giving 250W. This was the maximum they were allowed to install at the time as a domestic dwelling. The system cost £6,000. Mrs Kirrage says, "It was predicted to produce 4,074kW per annum. We haven't reached that total in a year yet but it is getting more and more each year."

They have endeavored to make their home as environmentally friendly as possible - with electric under floor heating throughout, powered by an air source heat pump and a rainwater harvester. They also have an MVHR - a mechanical ventilation heat recovery system, which extracts 'polluted' damp air from the kitchen and bathrooms and returns filtered fresh air - negating the need to open windows to dry out damp rooms. However they decided not to invest in a battery: 

"We do not have a battery. The advice was that we would not store enough power to make it worth the expense as we would use most, if not all, of what we generate. It is a large house and we are all electric. I last double checked about battery storage during lockdown and the advice was still the same.

"When we rebuilt large sections of the house in 2015, we did all that we could to make it environmentally friendly and cost effective to run. Our insulation is over and above the required amount at that time. All of our rainwater goes to a 3,200 litre tank and flushes the toilets and does the washing machine. However the pump for this uses electricity. The MVHR system is excellent at keeping the house well ventilated and making sure that condensation doesn't stand a chance, but it also runs on electricity. Our heating is all under floor and powered by a 15kW air source heat pump which again runs on electricity! So it's swings and roundabouts!" 

Janet did invest in an iBoost. This diverts unused excess solar-generated electricity towards the immersion heater to keep this topped up with hot water, before exporting anything to the grid. These can be used whether you have batteries or not. You can read about using one with a battery in Richard Moseley's case study. 

Their system is pre-apps and Mrs Kirrage has no way of knowing how much they are exporting to the grid. She was eligible for FiT payments based on their 4,074 units prediction. She receives 13.88p per kW and then another 4.7p per kW as an export tarif based on a prediction of exporting 50 percent of what she produces. This has and will continue for the 20 years since the panels were installed. 

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However Mrs Kirrage is able to tell that their annual generation from solar power is 3,982 units a year. They are heavy electric users and their annual consumption is 12,897 units: "We are all electric, the only gas is in the greenhouse keeping my winter plants warm!

"It's fair to say that the first few years it would probably have been cheaper to heat the house with gas, but it was obvious that gas boilers would be banned in time. Government has subsequently announced just that and the price of gas has increased massively, as has electricity. Factor in the cost of changing all the heating again and to my mind we made the right choice to go with the systems we have."